Deposition and Electrical Characterization of Very Thin SrTiO₃ Films for Ultra Large Scale Integrated Dynamic Random Access Memory Application

Abstract

SrTiO3 thin films are deposited on Pt/SiO2/Si substrates using RF magnetron sputtering in a temperature range from 200° C to 600° C. The film deposited at 600° C shows the best dielectric property and leakage current characteristics due to its good crystallinity and stoichiometric composition. Dielectric constant of the film deposited at 600° C decreases with decreasing thickness from 235 at 120 nm to 145 at 30 nm. Leakage current shows a constant value of about 30 nA/cm2 at 1.6 V in a thickness range from 50 nm to 120 nm but increases rapidly to 5 µ A/cm2 at 30 nm. The electrical properties of the films are explained by a model of the Pt/SrTiO3/Pt capacitor based on the band structure.

Study of leakage current in metal–insulator–metal Mg–Al co-doped barium strontium titanate thin films as a function of temperature and applied field

“…4a, the Mg-Al co-doped BST films have a lower leakage current density than only Mg-doped films in the electric field at temperature between 298 and 423 K. The leakage current increases with the measurement temperature and the Schottky emission (SE) mechanism may be adopted to explain the relationship between leakage current and temperature. Hwang et al [23] who stated that contacts between the Pt electrode and perovskite oxide thin films have Schottkytype characteristics because of the surface adsorptions and/or broken bonds on the surface. The intercepts of the curves measured for 5 mol% Mg-, 5 mol% Mg-1 mol% Al-, 5 mol% Mg-3 mol% Al-and 5 mol% Mg-5 mol% Al-co-doped BST films in an electric field of 150 kV/cm are − 9.37, − 9.23, − 9.16, and − 9.09 (A cm − 2 -K − 2 ) and slopes for above relation are − 5564.02, − 6096.58, − 6354.86 and − 6530.48, respectively.…”

Size effects on Pb0.5Ca0.5TiO3 thin films

“…The thickness of the interfacial layer (dead-layer) is close to the value for the depletion layer thickness estimated for Pt/SrTiO 3 /Pt capacitors (∼200Å). 9 It should be noted that consider the same K b value for all the thickness is a rough approximation because the temperature at maximum is increasing in decreasing the film thickness (Fig. 3b).…”

“…The contact potential between the ferroelectric and electrode can give rise to a deadlayer. 9 The total residual stress produced during the thin film preparation produce a lowering in the dielectric constant as well. 10 In the sol-gel film formation the sol-drying stresses are very large due to the strong mass loss produced.…”

“…Also a dc bias field can produce the same effects in ferroelectric materials and bias fields can be also be produced at the film/electrode interface. 9 Nevertheless, the shift of the dielectric constant maxima as well as the reduction in value should be related to the presence of dead-layer of lower dielectric constant produced among other factors by the relaxation of the stress induced during the sol-gel preparation. The possibility of existence of a chemical modified layer can be avoided as a result of the performed RBS analysis in films prepared in the same way and with the same composition.…”

Anisotropic electrical properties in bismuth layer structured dielectrics with natural super lattice structure

“…As alternatives, perovskite materials with a large dielectric constant over 200, such as (Ba,Sr)TiO 3 , have been widely considered to promote the high densification of the devices. [3][4][5][6] However, these materials show large deterioration in the dielectric constant with the decrease of the film thickness, so called "size-effect." These size-effects are, therefore, critical issues for the size scaling of the devices into nm-scale.…”